FEATURES
s
LT1769
Constant-Current/
Constant-Voltage 2A Battery
Charger with Input Current Limiting
DESCRIPTIO
The LT
®
1769 current mode PWM battery charger is a
simple, efficient solution to fast charge modern recharge-
able batteries including lithium-ion (Li-Ion), nickel-metal-
hydride (NiMH) and nickel-cadmium (NiCd) that require
constant-current and/or constant-voltage charging. The
internal switch is capable of delivering 2A** DC current
(3A peak current). Charge current can be programmed by
resistors or a DAC to within 5%. With 0.5% reference voltage
accuracy, the LT1769 meets the critical constant-voltage
charging requirement for Li-Ion cells.
A third control loop is provided to regulate the current
drawn from the input AC adapter. This allows simulta-
neous operation of the equipment and battery charging
without overloading the adapter. Charge current is reduced
to keep the adapter current below specified levels.
The LT1769 can charge batteries ranging from 1V to 20V.
Ground sensing of current is not required and the battery’s
negative terminal can be tied directly to ground. A saturat-
ing switch running at 200kHz gives high charging effi-
ciency and small inductor size. A blocking diode is not
required between the chip and the battery because the
chip goes into sleep mode and drains only 3µA when the
wall adapter is unplugged.
s
s
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Simple Solution to Charge NiCd, NiMH and Lithium
Rechargeable Batteries—Charging Current
Programmed by Resistors or DAC
Adapter Current Limit Allows Maximum Possible
Charging Current During System Use*
Precision 0.5% Accuracy for Voltage Mode Charging
Available in 20-Lead Exposed Pad TSSOP and
28-Lead Narrow SSOP Packages
High Efficiency Current Mode PWM with 3A Internal
Switch
5% Charge Current Accuracy
Adjustable Undervoltage Lockout
Automatic Shutdown When AC Adapter is Removed
Low Reverse Battery Drain Current: 3µA
Current Sensing Can Be at Either Terminal of the Battery
Charging Current Soft Start
Shutdown Control
APPLICATIO S
s
s
Chargers for NiCd, NiMH, Lead-Acid, Lithium
Rechargeable Batteries
Switching Regulators with Precision Current Limit
, LTC and LT are registered trademarks of Linear Technology Corporation.
*US patent number 5,723,970
**See LT1510 for 1.5A charger; see LT1511 for 3A charger
TYPICAL APPLICATIO
D1
††
SS24
R7
†
500Ω
GND
SW
BOOST
LT1769
COMP1
2nF
10k
SPIN
OVP SENSE
UV
PROG
V
C
BAT
R
S2
200Ω
1%
R3
+
390k
0.25%
BATTERY
VOLTAGE SENSE
R4
162k
0.25%
0.33µF
300Ω
C
PROG
1µF
R
PROG
4.93k
1%
CLP
CLN
V
CC
C1
1µF
C
IN
*
15µF
C2
0.47µF
L1**
22µH
D2
1N4148
NOTE: COMPLETE LITHIUM-ION CHARGER,
NO TERMINATION REQUIRED. R
S4
, R7
AND C1 ARE OPTIONAL FOR I
IN
LIMITING
*TOKIN OR UNITED CHEMI-CON/MARCON
CERAMIC SURFACE MOUNT
**22µH SUMIDA CDRH125
†
SEE APPLICATIONS INFORMATION FOR
INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT
††
GENERAL SEMICONDUCTOR. FOR T
J
LESS THEN 100°C
MBRS130LT3 CAN BE USED
R
S3
200Ω
1%
R
S1
0.05Ω
BATTERY CURRENT
SENSE
C
OUT
22µF
TANT
Figure 1. 2A Lithium-Ion Battery Charger
U
U
U
D3
††
SS24
R
S4
†
ADAPTER
CURRENT SENSE
†
V
IN
(ADAPTER INPUT)
11V TO 28V
TO MAIN
SYSTEM LOAD
R5
UNDERVOLTAGE
LOCKOUT
R6
5k
V
BAT
8.4V
Li-Ion
1511 • F01
1769fa
1
LT1769
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
Supply Voltage
(V
CC
, CLP and CLN Pin Voltage) ......................... 30V
BOOST Pin Voltage with Respect to V
CC
................. 25V
I
BAT
(Average)........................................................... 2A
Operating Junction Temperature Range
Commercial ........................................... 0°C to 125°C
Industrial ......................................... – 40°C to 125°C
Operating Ambient Temperature
Commercial ............................................ 0°C to 70°C
Industrial ........................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
GND**
GND**
GND**
SW
BOOST
UV
GND**
GND**
OVP
1
2
3
4
5
6
7
8
9
28 GND**
27 GND**
26 GND**
25 V
CC1
*
24 V
CC2
*
23 V
CC3
*
22 GND**
21 PROG
20 V
C
19 UV
OUT
18 COMP2
17 BAT
16 SPIN
15 GND**
ORDER PART
NUMBER
LT1769CGN
LT1769IGN
SW
BOOST
UV
GND
GND
OVP
1
2
3
4
5
6
7
8
9
CLP 10
CLN 11
COMP1 12
SENSE 13
GND** 14
GN PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 35°C/ W**
*ALL V
CC
PINS SHOULD
BE CONNECTED
TOGETHER CLOSE TO
THE PINS
** ALL GND PINS ARE
FUSED TO INTERNAL DIE
ATTACH PADDLE FOR
HEAT SINKING. CONNECT
THESE PINS TO
EXPANDED PC LANDS
FOR PROPER HEAT
SINKING. 35°C/W
THERMAL RESISTANCE
ASSUMES AN INTERNAL
GROUND PLANE
DOUBLING AS A HEAT
SPREADER
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 16V, V
BAT
= 8V, R
S2
= R
S3
= 200Ω (see Block Diagram),
V
CLN
= V
CC
. No load on any outputs unless otherwise noted.
PARAMETER
Overall
Supply Current
Sense Amplifier CA1 Gain and Input Offset Voltage
(With R
S2
= 200Ω, R
S3
= 200Ω)
(Measured across R
S1
)(Note 2)
V
PROG
= 2.7V, V
CC
≤
20V
V
PROG
= 2.7V, 20V < V
CC
≤
25V
8V
≤
V
CC
≤
25V , 0V
≤
V
BAT
≤
20V
R
PROG
= 4.93k
R
PROG
= 49.3k
T
A
< 0°C
V
CC
= 28V, V
BAT
= 20V
R
PROG
= 4.93k
R
PROG
= 49.3k
T
A
< 0°C
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
2
U
U
W
W W
U
W
TOP VIEW
20 GND
19 V
CC1
18 V
CC2
17 V
CC3
16 PROG
15 V
C
14 GND
13 UV
OUT
12 BAT
11 SPIN
ORDER PART
NUMBER
LT1769CFE
LT1769IFE
CLN
CLP
COMP1
SENSE 10
FE PACKAGE
20-LEAD PLASTIC TSSOP
†
THE BOTTOM METAL
T
JMAX
= 125°C,
θ
JA
= 35°C/ W
†
EXPOSED PAD IS GROUND
(MUST BE SOLDERED TO PCB)
EXPOSED PAD SIZE: 3.0
×
4.1
(.188) (.162)
PLATE OF THIS PACKAGE
IS FUSED TO INTERNAL
GROUND AND IS FOR
HEAT SINKING. SOLDER
THE BOTTOM METAL
PLATE ONTO PCB
GROUND PLANE FOR
HEAT SINKING.
MIN
TYP
4.5
4.6
MAX
6.8
7.0
107
12
13
110
13
14
UNITS
mA
mA
mV
mV
mV
mV
mV
mV
1769fa
93
8
7
90
7
6
100
10
q
q
LT1769
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 16V, V
BAT
= 8V, R
S2
= R
S3
= 200Ω (see Block Diagram),
V
CLN
= V
CC
. No load on any outputs unless otherwise noted.
PARAMETER
Overall
V
CC
Undervoltage Lockout (Switch OFF) Threshold
UV Pin Input Current
UV Output Voltage at UV
OUT
Pin
UV Output Leakage Current at UV
OUT
Pin
Reverse Current from Battery (When V
CC
Is
Not Connected, V
SW
Is Floating)
Boost Pin Current
Measured at UV Pin
0.2V
≤
V
UV
≤
8V
In Undervoltage State, I
UVOUT
= 70µA
8V
≤
V
UV
, V
UVOUT
= 5V
V
BAT
≤
20V, V
UV
≤
0.4V
V
CC
= 20V, V
BOOST
= 0V
V
CC
= 28V, V
BOOST
= 0V
2V
≤
V
BOOST
– V
CC
< 8V (Switch ON)
8V
≤
V
BOOST
– V
CC
≤
25V (Switch ON)
8V
≤
V
CC
≤
V
MAX
, I
SW
= 2A,
V
BOOST
– V
SW
≥
2V
V
BOOST
= 24V, I
SW
≤
2A
V
SW
= 0V, V
CC
≤
20V
20V < V
CC
≤
28V
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
6
TYP
7
0.1
0.1
0.1
3
0.1
0.25
6
8
MAX
8
5
0.5
3
15
10
20
9
12
UNITS
V
µA
V
µA
µA
µA
µA
mA
mA
Switch
Switch ON Resistance
∆I
BOOST
/∆I
SW
During Switch ON
Switch OFF Leakage Current
Minimum I
PROG
for Switch ON
Minimum I
PROG
for Switch OFF
Maximum V
BAT
for Switch ON
Current Sense Amplifier CA1 Inputs (Sense, BAT)
Input Bias Current
Input Common Mode Low
Input Common Mode High
SPIN Input Current
Reference
Reference Voltage (Note 3)
Reference Voltage
Oscillator
Switching Frequency
Switching Frequency
Maximum Duty Cycle
q
q
q
q
q
q
q
0.15
25
2
4
2
1
4
2.4
0.25
35
100
200
20
V
CC
– 2
Ω
mA/A
µA
µA
µA
mA
V
µA
V
V
µA
– 50
– 0.25
– 125
V
CC
– 2
– 100
R
PROG
= 4.93k, Measured at OVP with
VA Supplying I
PROG
and Switch OFF
All Conditions of V
CC
, T
A
≥
0°C
T
A
< 0°C (Note 4)
q
q
– 200
2.448
2.441
2.43
180
2.465
2.477
2.489
2.489
V
V
V
kHz
kHz
kHz
%
%
200
200
93
220
230
230
All Conditions of V
CC
, T
A
≥
0°C
T
A
< 0°C
q
q
170
160
90
85
150
Current Amplifier CA2
Transconductance
Maximum V
C
for Switch OFF
I
VC
Current (Out of Pin)
V
C
≥
0.6V
V
C
< 0.45V
V
C
= 1V, I
VC
=
±1µA
q
250
550
0.6
100
3
µmho
V
µA
mA
1769fa
3
LT1769
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 16V, V
BAT
= 8V. No load on any outputs unless otherwise noted.
PARAMETER
Voltage Amplifier VA
Transconductance (Note 3)
Output Source Current
OVP Input Bias Current
Output Current from 50µA to 500µA
V
OVP
= V
REF
+ 10mV, V
PROG
= V
REF
+ 10mV
VA Output Current at 0.5mA
VA Output Current at 0.5mA, T
A
> 90°C
VA Output Current at 0.5mA, T
A
< 0°C
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
MAX
UNITS
0.25
1.1
0.6
±3
1.3
±10
25
±15
mho
mA
nA
nA
nA
–15
Current Limit Amplifier CL1, 8V
≤
Input Common Mode
Turn-On Threshold
Transconductance
CLP Input Current
CLN Input Current
0.5mA Output Current
Output Current from 50µA to 500µA
0.5mA Output Current, V
UV
≥
0.4V
0.5mA Output Current V
UV
≥
0.4V
93
0.5
100
1
0.3
0.8
110
2
1
2
mV
mho
µA
mA
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Tested with Test Circuit 1.
Note 3:
Tested with Test Circuit 2.
Note 4:
A linear interpolation can be used for reference voltage
specification between 0°C and – 40°C.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency of Figure 1 Circuit
100
98
96
94
6
V
IN
= 16.5
V
BAT
= 8.4V
8
7
EFFICIENCY (%)
I
CC
(mA)
90
88
86
84
82
80
0.2
0.6
CHARGER EFFICIENCY
T
J
= 0°C
4
3
I
CC
(mA)
92
INCLUDES LOSS
IN DIODE D3
1.0
1.4
I
BAT
(A)
4
U W
1.8
1769 G01
I
CC
vs Duty Cycle
7.0
V
CC
= 16V
I
CC
vs V
CC
MAXIMUM DUTY CYCLE
T
J
= 0°C
T
J
= 25°C
6.5
5
T
J
= 125°C
T
J
= 25°C
6.0
T
J
= 125°C
5.5
2
1
0
2.2
0
10
20
5.0
4.5
30 40 50 60
DUTY CYCLE (%)
70
80
0
5
10
15
V
CC
(V)
20
25
30
1769 G03
1769 G02
1769fa
LT1769
TYPICAL PERFORMANCE CHARACTERISTICS
V
REF
Line Regulation
0.003
0.002
3
4
0.001
∆V
REF
(V)
0
∆V
OVP
(mV)
–0.001
1
–0.002
–0.003
0
0
5
Maximum Duty Cycle
98
97
96
–1.20
–1.08
–0.96
–0.84
–0.72
DUTY CYCLE (%)
95
I
VC
(mA)
94
93
92
91
90
0
20
120
JUNCTION TEMPERATURE (°C)
40
60
80
100
140
PROG Pin Characteristics
6
T
J
= 125°C
REFERENCE VOLTAGE (V)
I
PROG
(mA)
0
–6
0
1
2
3
V
PROG
(V)
4
5
1769 G08
U W
10
I
VA
vs
∆V
OVP
(Voltage Amplifier)
ALL TEMPERATURES
2
T
J
= 125°C
T
J
= 25°C
15
V
CC
(V)
20
25
30
1769 G04
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
I
VA
(mA)
1769 G05
V
C
Pin Characteristics
–0.60
–0.48
–0.36
–0.24
–0.12
0
0.12
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
V
C
(V)
1769 G07
1769 G06
Reference Voltage
vs Temperature
2.470
2.468
2.466
2.464
2.462
2.460
2.458
0
25
125
50
75
100
JUNCTION TEMPERATURE
150
T
J
= 25°C
1769 G09
1769fa
5
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